All-conjugated block copolymers for efficient and stable organic solar cells with low temperature processing

Tyagi, P., Hua, S.-C., Amorim, D. R., Faria, R.M., Kettle, J. and Horie, M. (2018) All-conjugated block copolymers for efficient and stable organic solar cells with low temperature processing. Organic Electronics, 55, pp. 146-156. (doi: 10.1016/j.orgel.2018.01.032)

Abstract

The low embodied energy within Organic Photovoltaics (OPVs) provides the technology with a characteristic that surpasses all other PV materials. In this work, all-conjugated block copolymers comprising of P3HT and PTB7-Th have been synthesized which enable even lower temperature processibility, thus reducing the embodied energy further. The all-conjugated block copolymers comprise of P3HT and poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th). To synthesis these, a narrow-distributed, monobrominated P3HT (Mn = 7000, Mw/Mn = 1.31) is synthesized by Grignard metathesis polymerisation. This is further reacted with distannyl and dibromo monomers of PTB7-Th by Stille step-growth polycondensation to provide the block copolymers of P3HT-b-PTB7-Th. In these reactions, block ratios are adjusted to 1 to 2 and 1 to 10 based on the numbers of the repeating units of the monomers (i.e. 3-hexylthiophene unit: two monomers of PTB7-Th = 1:2 and 1:10). The block copolymer showed hole mobility of 5.9 × 10−5 cm2/Vs. The highest power conversion efficiency of 3.6%, which was achieved with the photoactive layer processed at 60 °C, which is substantially lower than the annealing temperature needed for standard P3HT-based solar cells. Furthermore, the stabilised lifetime of encapsulated devices is enhanced compared to P3HT and PTB7-Th devices, with no drop in efficiency noted for 7 days after initial burn in process.

• Item Type: Articles
• Additional Information: The authors would like to acknowledge the European Regional Development Fund (ERDF) and the Welsh European Funding Office (WEFO) for funding the 2nd Solar Photovoltaic Academic Research Consortium (SPARC II). This work was financially supported by Ministry of Science and Technology, Taiwan and Frontier Research Center on Fundamental and Applied Sciences of Matters at National Tsing Hua University Taiwan.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Kettle, Professor Jeff
• Authors: Tyagi, P., Hua, S.-C., Amorim, D. R., Faria, R.M., Kettle, J., and Horie, M.
• College/School: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Journal Name: Organic Electronics
• Publisher: Elsevier
• ISSN: 1566-1199
• ISSN (Online): 1878-5530
• Published Online: 25 February 2018